1. Field of the Invention
The present invention relates to a support structure for a clutch hub used in an engaging device of a change-gear mechanism of an automatic transmission, in particular, a clutch hub having an outer cylindrical portion that engages with friction plates, and a bottom wall that engages at its central portion with another rotating member.
2. Description of the Prior Art
A change-gear mechanism of an automatic transmission is adapted to establish a plurality of gear positions by selectively engaging or releasing rotating elements linked with a plurality of gears in different combinations. The rotating elements may be engaged with or disengaged from each other by means of a clutch having a plurality of ring-like friction plates on each of its driving side and driven side, and the plural friction plates on one of the drive and driven sides are supported by a drum-like clutch hub having a cylindrical shape with a bottom, while the friction plates on the other side are supported by a drum-like rotating member.
On the driven side of the clutch, for example, axial splines are formed on the outer circumferential surface of a cylindrical portion of the clutch hub, and a plurality of driven-side friction plates having inner teeth are axially movably supported by the clutch hub, with the inner teeth held in engagement with the splines of the clutch hub. On the driving side, on the other hand, axial splines are formed on the inner circumferential surface of the drum-like rotating member, and a plurality of driving-side friction plates having outer teeth are axially movably supported by the rotating member, with the outer teeth held in engagement with the splines of the rotating member.
The clutch hub as described above is connected at a radially inner portion thereof on the center side of the bottom wall, with another rotating member. In the case of an overrun clutch, for example, the clutch is combined with a one-way clutch, so as to establish a selected one of a mode that permits overrunning of an output shaft of the transmission thereby to achieve the feeling of smooth running, and a mode that provides an engine brake effect.
Conventionally, the clutch hub of the overrun clutch and the one-way clutch are connected to each other as shown in FIG. 3. The clutch hub 51 of the overrun clutch 50 has a through hole 57 which is formed through a central portion of its bottom wall 53, to allow the output shaft 10 to pass therethrough. The bottom wall 53 also has a notch or hole 54 in the vicinity of the through hole 57. The one-way clutch 60 has an inner race 61 which is formed with a protrusion 62 that extends from one end face of the inner race 61 in the axial direction. This protrusion 62 engages with the hole 54 of the bottom wall 53, to be connected to the clutch hub 51, so that the clutch hub 51 and the inner race 61 are rotated together as a unit.
In the known connecting structure around the clutch hub, however, a certain clearance is present between the inner wall of the through hole 57 of the bottom wall 53 of the clutch hub and the output shaft 10, and a substantial radial clearance is also present between the protrusion 62 of the inner race 61 and the hole 54 of the clutch hub 51. With these clearances thus formed, the clutch hub 51 and the friction plates are automatically aligned with each other when the clutch hub 51 is rotated. Upon start of rotation of the clutch, however, the clutch hub 51 is displaced in the radial direction, and misalignment occurs between the bottom wall 53 of the clutch hub 51 and a thrust bearing 58 located between the bottom wall 53 and an adjacent rotating member 46, thus causing a problem that a case 59 for holding the bearing is twisted and stressed, and is likely to wear in an early period of use.
The through hole 57 of the clutch hub 51 through which the output shaft 10 is inserted is merely formed through the bottom wall 53 having a small thickness, and it is thus difficult to maintain the posture of the clutch hub 51 only by means of the output shaft 10. When the clutch hub 51 is not rotated, therefore, the clutch hub 51 is inclined relative to the output shaft 10. Accordingly, the clutch hub 51 undergoes changes in its posture, in addition to the above-described displacement in the radial directions each time the clutch starts being rotated or stops being rotated, which also accelerates wear of the thrust bearing 58.